The present invention relates to an automatic call transfer circuit comprising a plurality of telephones which are connected in parallel respectively between a pair of telephone lines for a selective use thereof.
A call transfer switch for a selective use of a pair of telephones is well known, which is suitable for a secret conversation. But, the call transfer switch is very bothersome in the operation thereof.
A branch system of a plurality of telephones is also used, which is not bothersome. But, the branch system of a plurality of telephones does not permit a secret conversation.
The inventor has made and tested various automatic call transfer circuits for a plurality of telephones. But, there are two problems. One of the problems is that a telephone conversation may be cut off at a time of call transfer between the telephones and becomes a finished condition. The other one of the problems is a large noise is heard by a receiver of a telephone which is engaged to one of the telephones of the device at a moment of call transfer between the telephones of the circuit.